The invention relates to a regulating device for adjusting a regulating member, more particularly, to a rotary regulator for regulating the angle of rotation of a throttle member that determines a passage cross-section in a flow line of an internal combustion engine.
Examples of these regulating devices are used a so-called idle regulators in control systems of internal combustion engines in which, for example, a throttle member is mounted in a by-pass line associated with the internal combustion engine intake pipe; said throttle member, in turn, determines a mean cross-section of the by-pass line. Idle regulators of the said type are designed as so-called single winding regulators (SWR) or double winding regulators (DWR). An example of SWR is described in German patent 37 43 309 A1 and an example of a DWR is described in German patent 28 12 292 C2.
In the case of the aforementioned regulators, when problems occur in the control system, the throttle member adopts an emergency position in which overspeeding of the engine is prevented as a result of a predetermined passage cross-section of the by-pass line and continued operation of the internal combustion engine is ensured in a so-called emergency mode. In this emergency position of the throttle member, the passage cross-section of the by-pass line is generally only open 1/4 to 1/2 of the maximum passage cross-section. The throttle member or restoring member is moved into its emergency or starting position which is essential to the safe operation of the engine by the restoring device.
In a known regulating device of the above-described type (German patent 32 00 096 A1) the restoring device comprises a spiral spring which permanently influences the drive and thus directly acts on the regulating member. The restoring force of the spring is substantially less than the restoring force of the control drive and accordingly, during normal uninterrupted operation of the control drive the regulating member can be regulated by the control drive in opposition to the restoring force of the spring. However, when the restoring force of the control drive is removed, for example, as a result of an interruption in the power supply, the spring moves the regulating member into the emergency position.
To ensure reliable operation it is necessary for the spring to be relatively powerful in order that the emergency cross-section obtained when the regulating member is in the emergency position is reliably ensured. Accordingly, the electrical control drive must be provided with a relatively large output winding. As a result, the cross-sectional area of passage opened by the regulating member is dependent on the battery voltage and the external temperature. For example, when the battery voltage is low or the outside temperature is very low it is not possible to obtain the maximum opening cross-section in the by-pass line. Furthermore, the restoring device comes into operation when the electrical control, function of the control drive fails but not when there is a short circuit. When a short circuit occurs the regulating member fully opens the cross-sectional area of passage. The internal combustion engine is suddenly accelerated and runs at high speeds.